Cam shaft

ABSTRACT

The instant invention relates to a cam shaft ( 1 ) for internal combustion engines of motor vehicles, which is supported on a cylinder head housing ( 15 ) via at least one roller bearing ( 2 ), wherein provision is made for at least one thrust bearing ( 3 ), which supports the cam shaft ( 1 ) in axial direction ( 4 ) and which is embodied as ball or also as roller bearing ( 2 ).

The invention relates to a cam shaft for internal combustion engines ofmotor vehicles, which is supported on a cylinder head housing via atleast one roller bearing.

Typically, cam shafts are supported in cam shaft bearings, which arenormally manufactured as bushings made from materials, such as aluminumalloys, for example, or as half bearings made of materials on the basisof copper alloys. However, other types of bearings, such as a rollerbearing, for example, are also known from the state of the art. A thrustbearing function for the cam shaft is normally taken over via aso-called washer disk, which is also known as “trust plate”. However, ascompared to other bearing devices, such washer disks have a considerablyshorter life expectancy so that they must typically be replaced on arotational basis.

The invention deals with the problem of specifying an improvedembodiment for a cam shaft, where in particular a thrust bearing isimproved.

This problem is solved according to the invention by means of the objectof independent claim 1. Advantageous embodiments are the object of thedependent claims.

The invention is based on the general idea of embodying a thrust bearingfor a cam shaft for internal combustion engines of motor vehicles asball bearings or as roller bearings and to thus on the one handconsiderably extend the life expectancy of the thrust bearing and tothus on the other hand improve the thrust bearing as a whole. At thesame time, the cam shaft supported in axial direction in such a mannercan be supported on a cylinder head via further bearing devices, whichare embodied as roller bearings, whereby the entire bearing of the camshaft can be improved as compared to bearings known from the state ofthe art.

In an advantageous development of the solution according to theinvention, at least one thrust bearing, which is embodied as a rollerbearing, encompasses a roller, which runs directly on the cam shaft,wherein a region of the cam shaft, which comes into contact with theroller, is hardened. Through this, a particularly effective bearing ofthe cam shaft can be attained, wherein a hardening of the region, whichcomes into contact with the roller, can be hardened via an inductive andthus highly pinpointed heating, for example, as well as via a subsequentrapid cooling. The hardening thereby increases the wear resistance ofthe cam shaft, whereby the life expectancy thereof can be extended.

As an alternative thereto, provision can be made in a further embodimentin the region of the thrust bearing, which is embodied as rollerbearing, for a bushing, which is arranged directly on the cam shaft andon which the roller of the roller bearing rolls. Such a bushing can alsobe hardened, for example, and can thus encompass a considerably improvedwear resistance as compared to an unhardened material. At the same time,such a bushing can be chosen in such a manner with reference to itsmaterial characteristics that particularly good bearing characteristicscan be attained.

Advantageously, the cams and/or the roller bearing and/or the at leastone thrust bearing are connected to the cam shaft by means of a thermaljoining process, by means of an interference fit assembly or by means ofadhesion, wherein only finished cams and/or roller bearings and/orthrust bearings are used for joining with the cam shaft. Due to thefinished components, a machine finishing of the cams and of the camshaft, respectively, is not necessary after connecting theafore-mentioned components to the cam shaft, whereby it can be preventedthat swarf, for example, penetrates into the roller bearings andnegatively impacts them during the future operation.

Advantageously, the at least one thrust bearing, which is embodied as aball or roller bearing, is arranged between two cams of the cam shaftand is directly supported thereon. The thrust bearing is thus fixedbetween the two cams with reference to its axial direction, withoutrequiring further fixing elements for this purpose, the production ofwhich is extensive, for example. It is also possible for the at leastone thrust bearing, which is embodied as a ball or roller bearing, to beindirectly supported on the two cams via two spacer elements, inparticular via two spacer bushings. Such spacer bushings provide thelarge advantage that the thrust bearing must not necessarily be arrangedin the region directly next to the cams, but that, depending on theaxial length of the chosen bushing, it can be arranged in a location,which is advantageous for the installation of the thrust bearing. In thealternative, these spacer bushings can also be fixedly connected to theadjacent cams, which entails a shortened assembly time for the camshaft.

Advantageous exemplary embodiments, which will be defined below, areillustrated in the drawings.

In each case in a schematic view,

FIG. 1 shows a cam shaft according to the invention,

FIG. 2 a to d show different embodiments of thrust bearings, which areembodied as ball bearings,

FIG. 3 shows a possible embodiment of thrust bearings of a cam shaftwhen assembled,

FIG. 4 shows a sectional view through a cam shaft comprising a thrustbearing according to the invention,

FIG. 5 shows a detailed view of a thrust bearing according to theinvention,

FIG. 6 shows a view onto a cam shaft according to the invention,

FIG. 7 shows a view onto a cam shaft according to the invention,

FIG. 8 shows a radial bearing embodied as a roller bearing,

FIG. 9 shows an illustration as in FIG. 8, however in a differentembodiment,

FIG. 10 shows a thrust bearing (held in position by means of frictionalconnection) embodied as a roller bearing,

FIG. 11 to 13 show a sectional view through a cam shaft according to theinvention in a respective other embodiment.

According to FIG. 1, a cam shaft 1 for internal combustion engines ofmotor vehicles according to the invention encompasses at least oneroller bearing 2, via which the cam shaft 1 is supported on anon-illustrated cylinder head housing 15. Furthermore, the cam shaft 1encompasses at least one thrust bearing 3, which supports the cam shaft1 in axial direction 4 and which is embodied as a ball or as a rollerbearing. The cam shaft 1 according to FIG. 1 is a cam shaft for enginescomprising a so-called “tunnel bearing”. That is to say, the cam shaft 1is inserted into the cam shaft bearing of the crank case in thedirection of the cam shaft axis 4.

According to FIG. 2 a to 2 d, different embodiments of the thrustbearings 3, which are embodied as ball bearings, are illustratedthereby. FIG. 2 a shows a thrust bearing 3 embodied as a ball bearing,which is arranged in axial direction 4 between two cams 5 and 5′ andwhich is indirectly supported on the cams 5, 5′ via two spacer bushings6, 6′. The spacer bushings 6, 6′ can thereby generally also be referredto as spacer elements.

Contrary thereto, FIG. 2 b shows a thrust bearing 3, which is alsoarranged between two cams 5 and 5′, which, however, is directlysupported on the adjacent cams 5, 5′, namely in each case via a collar7, 7′, which is a component of the cams 5, 5′. The collar 7, 7′ in FIG.2 b thereby performs the task of the spacer bushings 6, 6′ in FIG. 2 a.

A part 8 (bushing) of the thrust bearing 3 on the cam shaft side inaxial direction is embodied in FIG. 2 c to be so wide that the thrustbearing 3 can also be directly supported on the adjacent cams 5 and 5′.

FIG. 2 d shows an embodiment, where the thrust bearing 3, which isembodied as a ball bearing, is also located between two cams 5 and 5′ ofthe cam shaft 1 and is supported on a collar 7 a and 7 b of the cams 5and 5′, wherein the respective collar 7 a and 7 b is not a component ofthe cam 5 and 5′, but is soldered, welded or adhered thereto.

FIG. 4 illustrates a cam shaft 1 in a sectional view, wherein the rollerbearings 2 as well as the at least one thrust bearing 3 can beidentified well.

In the thrust bearing 3 according to FIG. 1 to 6, the thrust bearing 3is embodied as a ball bearing and encompasses a bearing ring 9, at theouter jacket surface 10 of which provision is made for a revolvinggroove 11, which meshes with a connecting element 12, in particular astud screw or a pin, at the side of the cylinder head and thus fixes thecam shaft 1 in axial direction 4.

This can be identified particularly well in FIG. 5, wherein theconnecting element 12 is embodied herein as a stud screw and meshes withthe groove 11 of the bearing ring 9. A particularly clear illustrationof the groove 11, which is arranged on the bearing ring 9, is shown inFIG. 6.

Contrary thereto, the cam shaft 1 according to FIG. 7 does not encompassa thrust bearing 3, which is embodied as a ball bearing, but a thrustbearing according to FIG. 8 to 10, which is embodied as a rollerbearing.

According to FIG. 8, the at least one radial bearing, which is embodiedas a roller bearing, encompasses a roller 13, which runs directly on thecam shaft 1, wherein the region 14 of the cam shaft 1, which comes intocontact with the roller 13, is hardened. Contrary thereto, provision ismade with the thrust bearing 3 according to FIG. 9 in the region 14 ofthe thrust bearing 3, which is embodied as roller bearing, for a bushing8, which is arranged directly on the cam shaft 1, on which the roller 13of the roller bearing, that is to say the radial bearing, rolls. It goeswithout saying that the bushing 8 can also be made of a particularlywear-resistant material or can be subjected to an aging process, whichincreases the wear-resistance.

FIG. 11 to 13 once again show the thrust bearings 3 from FIG. 2 b to 2d, which are embodied as ball bearings, in their post-assembly position.

The cam shafts 1 according to FIG. 7 to 11 are cam shafts 1 for enginescomprising a so-called “open bearing”. That is to say, the cam shaft 1is held in position in the cam shaft bearing of the cylinder head 15parallel to the cam shaft axis 4 and by means of bearing caps.

As a matter of principle, the cams 5 and/or the roller bearing 2 and/orthe at least one thrust bearing 3 in the cam shaft 1 according to theinvention are connected to the cam shaft 1 by means of a thermal joiningprocess, by means of an interference fit assembly or by means ofadhesion. It is thereby particularly advantageous that only finishedcams 5 and/or roller bearings 2 and/or thrust bearings 3 are used forjoining with the cam shaft 1 so that a finishing of the cam shaft 1 isno longer necessary after the application of the afore-mentionedcomponents and that swarf and processing dust, respectively, can thus beprevented from reaching into the bearings and thus from damaging them inthe long run.

The cam shaft 1 according to the invention makes it possible to replacea currently conventional washer disk, which is required for the thrustbearing of the cam shaft 1, with the thrust bearing 3 according to theinvention, which, on the one hand, encompasses a considerably higherlife expectancy and which, on the other, helps to reduce maintenancecosts in particular.

In a particularly preferred method for producing the cam shaft 1, closedroller bearings 2 are applied to said cam shaft 1 during the cam shaftassembly.

Either individually as well combined with one another in any manner, allof the features described in the description and in the following claimscan be substantial for the invention.

1-12. (canceled)
 13. A cam shaft assembly comprising: a cam shaft; at least one roller bearing for supporting the cam shaft in a first direction; and at least one thrust bearing for supporting the camshaft in a second direction, the thrust bearing including at least one of a ball bearing and a roller bearing.
 14. The cam shaft assembly of claim 13, wherein the second direction extends generally parallel to a longitudinal axis of the cam shaft.
 15. The cam shaft assembly of claim 13, further comprising: a bearing ring that engages the thrust bearing, the bearing ring including a circumferential groove; and a connecting element attached to a cylinder head of an internal combustion engine; wherein the circumferential groove of the bearing ring is engageable with the connecting element.
 16. The cam shaft assembly of claim 15, wherein the connecting element is at least one of a stud screw and a pin.
 17. The cam shaft assembly of claim 13, wherein the at least one roller bearing comprises at least one roller that directly engages the cam shaft.
 18. The cam shaft assembly of claim 17, wherein a region of the cam shaft that the roller directly engages is hardened.
 19. The cam shaft assembly of claim 13, further comprising a bushing directly engaging the cam shaft, wherein the at least one roller bearing comprises at least one roller directly engaging the bushing.
 20. The cam shaft assembly of claim 19, wherein the bushing is hardened.
 21. The cam shaft assembly of claim 19, wherein the bushing is joined to the cam shaft by at least one of adhesion, an interference fit, or welding.
 22. The cam shaft assembly of claim 13, further comprising at least two cams attached to the cam shaft, wherein the at least one thrust bearing is arranged between and engages the at least two cams.
 23. The cam shaft assembly of claim 13, further comprising: at least two cams attached to the cam shaft; and at least two spacers disposed between and engaging the at least two cams, wherein the at least one thrust bearing is arranged between and engages the at least two spacers.
 24. The cam shaft assembly of claim 13, further comprising at least two cams, each cam including a collar, wherein the at least one thrust bearing is arranged between the two cams and engages the collar of the at least two cams.
 25. The cam shaft assembly of claim 24, wherein the collar is integrally formed with the cam.
 26. The cam shaft assembly of claim 24, wherein the collar is attached to the cam by at least one of soldering, welding, and adhering.
 27. The cam shaft assembly of claim 13, further comprising at least one cam attached to the cam shaft by at least one of thermal joining, an interference fit, and adhesion.
 28. The cam shaft assembly of claim 13, wherein the at least one roller bearing is attached to the cam shaft by at least one of thermal joining, an interference fit, and adhesion.
 29. The cam shaft assembly of claim 13, wherein the at least one thrust bearing is attached to the cam shaft by at least one of thermal joining, an interference fit, and adhesion
 30. The cam shaft assembly of claim 13, wherein the camshaft is configured to be supported in an internal combustion engine in at least one of a tunnel bearing manner and an open bearing manner.
 31. The cam shaft assembly of claim 13, wherein the at least one roller bearing comprises a closed roller bearing attached to the cam shaft during assembly of the cam shaft assembly. 